(1) Field of the Invention
The present invention relates to a method and an apparatus for joining a protective adhesive tape to a semiconductor wafer surface on which a pattern is formed.
(2) Description of the Related Art
In a conventional producing process of a semiconductor wafer, a back surface of a semiconductor wafer (hereinafter, simply referred to as “wafer”) is processed using a mechanical method such as a grinding method and a polishing method, or a chemical method utilizing etching, and the thickness of the wafer is reduced. When the wafer is processed using such methods, in order to protect a surface on which a pattern is formed, a protective adhesive tape is joined to the surface.
That is, a wafer is transferred to a back grind process, and a surface thereof (pattern surface) is sucked and held by a chuck table and is ground by a grindstone. Herein, a stress is applied to the surface of the wafer due to the grinding operation, so that there is an adverse possibility that the pattern is damaged or contaminated. Therefore, a protective adhesive tape is joined to the surface.
In the case where the adhesive tape is joined to the surface of the wafer, generally, the adhesive tape is joined to the wafer from its end by rotating a roller and, then, an outer peripheral edge of the wafer is cut along the wafer by a cutting tool.
In recent years, there are increasing tendencies to thin the wafers. With the tendencies, the strength and rigidity of the wafer are deteriorated and, when wafers are processed or transferred, they are prone to be damaged. Further, handling thereof is difficult due to bending or warpage of the wafer. Therefore, there is a tendency that a thick, hard and rigid adhesive tape is used for increasing the strength of the wafer and suppressing the warpage thereof (see JP-A 2003-209084).
The thick and rigid adhesive tape described in the above publication which is used in recent years is advantageous in reinforcing the wafer. However, when an unnecessary adhesive tape after the adhesive tape is joined to the wafer surface and is cut out along the outer peripheral edge is to be wound, a cut portion of the unnecessary adhesive tape is concentrated on its center portion depending upon the winding force, and the adhesive tape shrinks in its width direction. As a result, in the wound adhesive tape, center portions thereof are superposed on each other on a winding roller, so that the widths thereof are varied and wrinkle is generated. If the adhesive tape is joined to the wafer in such a state, there is a problem that bubbles are generated between the adhesive tape and the wafer or that a continuous processing can not be continued due to meandering of the adhesive tape.